Which of these best describes why certain bacteria have become resistant to penicillin? a) the penicillin in the 1970's was much weaker that the penicillin used today, thus it was not as effective. b) penicillin was not effective in treating any bacterial diseases, so the doctors had to find new treatments. c) these new bacterial strains came out of the jungles and forests already equipped to be penicillin-resistant. d) penicillin was so heavily prescribed by doctors that it led to certain, more fit, strains of bacteria to be able to survive.

Analogy- 1 is to arete as 5 is to cirque horn glacial valley hanging valley

What does it mean for a cell membrane to be selectively permable

Mouse liver cells were homogenized and the homogenate subjected to equilibrium density-gradient centrifugation with sucrose gradients. fractions obtained from these gradients were assayed for marker molecules (i.e., molecules that are limited to specific organelles). the results of these assays are shown in the figure. the marker molecules have the following functions: cytochrome oxidase is an enzyme involved in the process by which atp is formed in the complete aerobic degradation of glucose or fatty acids; ribosomal rna forms part of the protein-synthesizing ribosomes; catalase catalyzes decomposition of hydrogen peroxide; acid phosphatase hydrolysis monophosphoric esters at acid ph; cytidylyltransferase is involved in phospholipid biosynthesis; and amino acid permease aids in transport of amino acids across membranes. a) name the marker molecule and give the number of the fraction that is most enriched for each of the following cell components: lysosomes; peroxisomes; mitochondria; plasma membrane; rough endoplasmic reticulum; smooth endoplasmic reticulum.